The seriousness of a nodule of 10 millimeters or more in the breast should be determined on a case-by-case basis. If there is no significant growth or pain over a short period of time, it is generally not considered serious. If it grows rapidly within a short period of time, it is relatively more serious and further investigations such as mammogram and pathology are usually needed to clarify the nature of the nodule. Whether a breast nodule is serious or not usually has little to do with the size of the nodule, but depends mainly on the nature of the nodule. Both benign and malignant breast nodules can be large or small. For example, some patients may develop cystic breast hyperplasia before menstruation, which is usually characterized by breast swelling and pain, with palpable nodules the size of a grain of rice or the size of a fingertip in the breast. In most cases, a nodule over 10 mm is not serious. If it is accompanied by pain or grows faster within a short period of time, it is necessary to go to the hospital for a mammogram, pathology examination, etc. to determine whether it is malignant or benign. It is recommended that patients with nodules over 10 millimeters in the breast should go to the hospital in time to do relevant examinations, to clarify the cause of the disease and under the guidance of the doctor for reasonable treatment.